Screw driver



AlVlarh-Q, :1943.

#16 y l-1131; E;

J.H. GEMMELL. SCREWV DRIVER vFiled July 3o. 1940 ATTORNEY Patented Mar.9, 1943 UNITED STATES PATENT OFFICE SCREW DRIVER James H. Gemmell,Oakland, Calif.

Application July 30, 1940, Serial No. 348,392

3 Claims. `(Cl. 145-50) The present invention relates to screw driversof the screw holding type and is concerned more particularly with theprovision of an improved screw driver of this type which is economicalto manufacture and assemble, and is constructed to hold a screweffectively.

It is a general object of the invention, therefore, to provide animproved screw holding screw driver. Another object of the invention isto provide an improved screw holding screw driver which is constructedto facilitate economical production and assembly.

Another object of the invention is to provide an improved screw holdingscrew driver which is provided with screw engaging surfaces of a novelconstruction to enable maximum surface to surface contact between thedriver bit` and the screw slot.

l Other objects and advantages of the invention will be apparent fromthe `following description of a preferred embodiment thereof asillustrated in the accompanying drawing, in which:

Figure l is an elevational view of a screw driver constructed inaccordance with the instant invention;

Figure 2 is an enlarged view of the screw driver with `the handle shownin section;

Figure 3 is an enlarged view similar to Figure 2 but taken at rightangles thereto;

Figure 4 is an enlarged detail view showing the screw driver in screwholding relation with `a screw; y

Figure 5 is a transverse sectional view taken in a plane indicated bythe line 5-5 in Figure 3;

Figure 6 is a transverse sectional view taken in a plane indicated bythe line 6-6 in Figure 3;

Figure 7 is a transverse sectional view taken in a plane indicated bythe line I--l in Figure 3;

Figure 8 is a fragmentary sectional view illustratng a modified form ofconstruction; and

Figure 9 is a transverse sectonal view taken in a plane indicated by theline 9 9 in Figure 8.`

Referring to Figure l, the screw driver includes a tubular handle I0 inwhich a blade assembly including a head I I and a release rod I2 aremounted for sliding movement.

The blade assembly comprises opposed similar bit sections I6 (Figs. 1-3)which are blanked and formed from sheet metal stock. Each bit section I6includes an semi-cylindrical shank portion I1 adapted to engage areduced portion I8 of the release rod I2 and fit closely within thetubular handle I IJ. Each semi-cylindrical portion I'I is provided witha circumferentially extending locking ear I9 which extends into themating recess 2l of the cooperating bit section and which is formedinwardly from the curvature of the semicylindrical portion to engage ina locking groove 22 in the rod. The groove 22 in the rod is formedbetween portions I8 of the rod of the same diameter for engagement withthe semi-cylindrical portion I'I of the bit section.

From the semi-cylindrical portion I1 thereof, each bit section convergesradially inwardly to form a tapered portion 23 which has inner cam edges24- for cooperation with retaining and spreading pin 26 suitably securedas by riveting in diametric position in the tubular handle. The taperedportions 23 of the opposite bit sections terminate in heads 21 whichflare outwardly toa greater diameter` and then taper down to theV screwengaging ends.

The head portions 21 of the respective bit sections terminate in screwslot engaging ends 28 of special construction. The inner surfaces ofends 28 are preferably flat for flush engagement in the releasedposition of the tool as seen in Figure 2. The outer surfaces of ends 28are formed to provide a thinner section 29 in the bit closely adjacentbut spaced from the end edge. While it is preferred to form the surface29 with a radius, it may be formed in any other suitable manner toprovide a thinner section at a point spaced from the end of the screwengaging portion for cooperation with the walls of the screw slot whenthe bit sections "are engaged therewith. This condition is shown inFigure 4 where the substantial area of contact between the bit sectionsand the screw slot walls is clearly evident.

As shown, the release rod I2 is provided with an extension 3|, which inthe released position of the screw driver' engages pin 26, as shown inFigures 2 and 3 to provide a stop for the movement of the head of thescrew driver in one direction relative to the handle. Movement in theother direction is limited by the engagement of head portions 2l withthe end of the tube.

To assemble the bit sections on the head I2, theyare placed on the rodby substantially radial movement relative thereto with their bent earsI9 engaging in the groove 22 so that their semicylindrical portions II tthe reduced portion I8 of the rod snugly. The rod and head assem- I blyis then slid into the tube so that the bit sections are held on the rodby the tube which prevents the ears I9 from moving out of the grooveradial movement out of engagement therewith. The pin 26 is then insertedand fastened as by riveting to complete the assembly.

Figure 4 illustrates the engagement of the screw driver with a screw,which engagement is effected merely by pushing the screw Sii onto thebit sections, and continuing the pushing until the blade and release rodassembly telescopes inwardly with respect to the tubes. During thetelescoping movement engagement of pin 26 with the inner cam edges 2i ofthe bit sections causes expanding thereof so that the screw engagingends are forced outwardly into engagement with the opposite side wallsof the screw slot 3l. By providing thicker end edges for the screwengaging portions of the bit sections, a substantiallysurface-to-surface engagement can be established between the walls ofthe screw slot and the outer side faces of the bit sections, as seen inFigure 4l, where the curvature provided is slightly exaggerated. Thisenables a substantially greater frictional holding force to be exertedon the screw. Obviously where a screw driver is designed for aparticular size of screw, the angularity of the outer surface of the bitsection may be controlled to maintain a substantially glush engagementbetween the bit sections and the walls of the screw slots when lthe bitsections are flexed during expansion thereof while being engaged in ascrew.

igures 8 and 9 illustrate a modified form of construction which isgenerally similar to that described in connection with Figures l to 7,but varies therefrom in certain particulars. In the form shown inFigures 8 and 9, the bit sections liia are secured on the release rodl2a independently of the tubular handle Eta and the locking ears 19a notonly serve to lock the bits against endwise movement on the rod but alsoagainst radial movement relative thereto. As seen most clearly in Figure9, this is accomplished by eX- tending the locking ear ma tocircumferential length of slightly more than 90, so that the spacingbetween the end of ear lila and the opposite side edge of the bit isless than diameter'V of the reduced portion 22a of the rod E2G. The rod2a is provided with a tapered end portion ,3io which extends downwardlyfrom the lower reduced portion ltd In assembly, the bit sections !ia areplaced in mating engagement and Vthen slid endwise over the tapered endportions i l. A screw driver of the screw-engaging type @comprising atubular handle and a blade assembly mounted for telescoping movementwithin the handle, said blade assembly including a pair of opposite bitsections formed to provide complemental inter-engaging portions tofacilitate assembly in the desired relative positions and a rod forengagement by said portions, circumferential ears and opposed recesseson said bit sections, said ears having their ends formed i inwardly fromtheir general curvature, recess means on said rod for engagement by saidinwardly formed ends, and cam means carried by said handle and extendingbetween said bit sections to engage cam portions thereof upon movementoi said blade assembly within said handle and cause expansion of saidbit sections into holding engagement with a screw.

2. A screw driver of the screw-engaging type comprising a tubular handleand a blade assembly mounted for telescoping movement within the handle,said blade assembly including a pair of opposite bit sections formed toprovide complemental inter-engaging portions to facilitate assembly inthe desired relative positions and a rod r Vfor engagement by saidportions, circumferential ears and opposed recesses on said bitsections, said ears having their ends formed inwardly from their generalcurvature, recess means on said rod for engagement by said inwardlyformed ends, said ears serving rto prevent both endwise and radialmovement of said Vbit sections, and cam means carried by said handle andextending between said bit sections to engage cam portions thereof uponmovement of said blade assembly within said handle and cause expansionof said bit sections into `holding engagement with a screw. i

3. A screw driver of the screw-engaging type comprising a tubular handleand a blade assembly mounted for telescoping movement within the handle,said blade assembly including a pair of opposite bit sections formed toprovide screw engaging portions and with complemental interengagingportions to facilitate assembly in the desired relative positions, and aYrod for engagement by said portions, circumferential ears and opposedrecesses 'onsaid bit sections, said ears having their ends formedinwardly from their general curvature, recess means on said rod forengagement by said inwardly formed ends, and

means operable in response to relative endwise movement of said handleandY said blade assembly for spreading said screw-engaging portions intoholding engagement with a screw.

JAMES H. GEMMELL.

